Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H,W = list(map(int,input().split()))
L = [list(input()) for _ in range(H)]  #L[H][W]
s = sum(l.count('.') for l in L)
dd = [(0,1),(0,-1),(1,0),(-1,0)]

res = None
que = deque([(0,0,0)])
used = {(0,0)}
while que:
    i,j,cost = que.popleft()
    if i == H-1 and j == W-1:
        res = cost
        break
    for di,dj in dd:
        ni = i+di; nj = j+dj
        if not(0<=ni<H) or not (0<=nj<W) or L[ni][nj]=='#' or (ni,nj) in used:
            continue
        que.append((ni,nj,cost+1))
        used.add((ni,nj))
if res:
    print(s-res-1)
else:
    print(-1)